A conventional Ethernet system is shown in FIG. 1 wherein different Ethernets 1 and 2 (i.e., in different regions) are interconnected by at least one switch 3. Switch 3 is implemented as a network device comprising a plurality of ports. Whether the switch is comprised of a plurality of network devices or a single switch, the switch is still referred to as a “switch” throughout the specification as long as the communication means between switches is implemented as common Bridge Protocol Data Units (BPDUs).
Switch 3 acts to monitor data packets communicated between different network regions. When switch 3 has received a packet from a certain network, the controller of switch 3 may compare the destination address and source address of the packet with addresses recorded in address table 31 of a database. If the destination address of the packet is the same as that of terminal 4 in the same network, the packet is discarded (i.e., no transmission) for filtering the packet transmission. Otherwise, the source address of the packet is dynamically recorded in address table 31 if the source address of the packet is not found in the address table 31. In other words, the address table of the switch is employed to determine the path of packet switching. Currently, the setting procedure for an address table is implemented by adding a plurality of messages in a long MAC address. Typically, the user first enters such messages into terminals prior to downloading to the switch. Alternatively, the user may sequentially set a physical address and message thereof through the network management protocol. Such entry of messages and/or manual setting of addresses is disadvantageous because it is time consuming and prone to error.
Moreover, a typical switch has a learning capability. Hence, a switch administrator may not perform a locking on address table. As a result, the source address of an unauthorized terminal may occupy space in the address table without permission. Further, when the destination address of a packet received by the switch is not recorded in the address table (i.e., not learned by the switch), the packet may be sent to any of the other remaining ports. As a result, available bandwidth of switch is reduced.
Recently, applications of networks have extended to communities and families. In a typical example, each family having address table access capability is coupled to a port of a switch provided by the network system provider. Hence, a plurality of computers installed in each family may access the Ethernet through the port. However, it is a disadvantageous condition that a significant number of packets may be sent to the network for processing when there is no limitation (or no suitable limiting) by the network system provider on the number of online computers from one user end. As a result, the address table of switch may be completely occupied simultaneously, which in turn reduces available bandwidth. In an extreme condition, a large number of packets having different address tables created by a user may occupy all available space of the address table of the switch connected to the user. Worse, an undesired propagation of the packets is performed, resulting in a reduction of available bandwidth. This means that bandwidth available to other users is reduced or even services therefor are interrupted in a worst condition.
Address learning techniques of the current switch are comprised of the following:
1. A self learning capability of address provided by network administration software, which is advantageous for limiting a size of the address table of switch, but disadvantageous because it is unable to limit or adjust a size of the address table of the respective port.
2. An address learning capability provided by hardware of the switch, wherein each port only learns a received first source address, which is disadvantageous because it is impossible to adjust and control hardware of the switch when the switch is learning the number of addresses of each port. Further, an auto aging out timer may be provided, compounding the problem of adjusting and controlling the switch. If, for example, ten computers are owned by a family, only one computer is allowed to access network, and therefore, the switch can only learn one source address. As a result, only one computer may access the Ethernet during online service and the switch may delete addresses of the other computers unless they are used frequently.
Thus, it is desirable to provide a novel method for controlling number of address in address table of switch in order to overcome the above drawbacks of prior art.